Lint collecting and burning screen



Ndv. 17, 1970 BRlNKMAN EIAL 3,541,303

LINT COLLECTING AND BURNING SCREEN Filed Nov. 8. 1967 I 2 Sheets-Sheet 1g' INVENTORS 12 Y Charles Whi /mill? ATTORNEY 1970 'r. J. BRINKMAN ETAL3,541,303

LINT COLLECTING AND BURNING SCREEN Nov.

2 Sheets-Sheet 2 Filed Nov. 8. 1967 United States Patent LINT COLLECTINGAND BURNING SCREEN Thomas J. Brinkman, Dayton, Thomas H. Fogt, WestCarrollton, and Charles C. Whistler, Jr., Dayton, Ohio,

assignors to General Motors Corporation, Detroit,

Mich., a corporation of Delaware Filed Nov. 8, 1967, Ser. No. 681,325Int. Cl. Hb 3/10 U.S. Cl. 219-374 13 Claims ABSTRACT OF THE DISCLOSUREThis invention relates generally to lint collecting and burning screensand more particularly to a directly energized screen for collecting andburning lint.

The disposal of lint accumulated from clothes being dried in a dryer byburning it within the dryer is not new. In fact, the concept of directlyenergizing the lint collecting screen to burn the lint entrapped on itis not new. However, so far as we are aware, no present directlyenergized lint burning screen has been directed to solving the problemof drawing a large amount of current with the attendant problem ofmaterially reducing the voltage source somewhere within the dryer by theinclusion of a step-down transformer, usually with a high voltage ratio.

Accordingly, the object of this invention in one of its broadest aspectsis to provide a directly energized lint burning screen which drawsappreciably less current than those now available, or stated anotherway, which oifers more resistance than those now available.

Another object of our invention is to provide such a lint burning screenin which the pore size is sufiiciently small to entrap lint.

Another object of our invention is to provide a directly energized lineburning screen capable of entrapping lint and operating off householdcurrent without an intervening transformer.

Another object of our invention is to provide a directly energized lintburning screen having a widened mesh in the transverse direction toreduce its current requirements and a finer mesh in the longitudinaldirection to maintain adequate lint entrapping capabilities.

In another of its broadest aspects, the invention is directed toproviding such an elongated strip of lint entrapping and burning screenin a useable package size.

Another object of our invention is to provide a directly energizedelongated lint burning screen which requires no transformer, is capableof entrapping lint, and is in useable package size for incorporationinto clothes dryers.

Other objects and advantages of the invention will hereinafter becomemore fully apparent from the following description of the annexeddrawings, which illustrate preferred embodiments and wherein:

FIG. 1 is a schematic view of a clothes dryer partially broken away toshow a first embodiment of a directly energized lint burning screenpackage in accordance with one aspect of our invention and its relationto the other parts of a dryer.

FIG. 2 is a section taken along the line 22 of FIG. 1.

FIG. 3 is a section taken along the line 3-3 of FIG. 2.

FIG. 4 is a section taken along the line 44 of FIG. 2.

FIG. 5 is an enlarged schematic view of a directly energized lintburning screen used in the package shown in FIG. 1 and is used toillustrate another aspect of our invention.

FIG. 6 is a frontal view of another embodiment of our invention.

FIG. 7 is a section taken along the line 77 of FIG. 6.

Referring now more particularly to FIG. 1, it shows a dryer indicatedgenerally at 10 having a cabinet 12 in which is rotatably mounted a drum14. An inlet in the back of the cabinet admits air to the perforate backof the drum through suitable inlet ducting in which is located the dryerheater. From the drum 14, the air exits out the access opening 16 intotransition duct 20 through holes in the port plate 18.

The lint burning chamber 22 is located downstream of the transition duct20 and is connected to a short tubular extension 24 of it. The chamber22 has a lint burning screen assembly indicated generally at 26extending across it transverse to the direction of air flow. A pivotallymounted damper 28 is shown in its closed position blocking off the inletto the chamber 22. The chamber outlet 30 is connected by a flexibleconduit 32 to the suction side of a fan 34 which exhausts the airthrough a suitable conduit 36 to the outside of the cabinet. A seconddamper 38 is mounted adjacent the outlet 30. It is connected by a commonlinkage 40 to a drive source 42 so that the dampers move in unison. Itis preferable that the damper 28 be movable to a fully closed position;however, the damper 38 may be movable between an open and a partiallyclosed, flow restricting position rather than a fully closed position.The fan 34 is directly driven and drum 14 is belt driven from the dryermotor. The structural details of the belt drive, the motor, the airinlet path with its heater have been omitted for clarity.

In one of its aspects, this invention is directed to a directlyenergized lint burning screen assembly 26 which is suitable for but notlimited to use in the lint burning system just briefly described andmore fully disclosed in copending US. patent application Ser. No.681,392, filed on Nov. 8, 1967 in the names of Thomas J. Brinkman,Thomas H. Fogt, George B. Long and Charles C. Whitler, Jr. and assignedto the assignee of the present invention.

Turning momentarily away from the screen assembly 26, another aspect ofthe present invention will be discussed in connection with FIG. 5. Byway of background, it is desirable to provide a directly energizedscreen which minimizes the current requirements so as to eithereliminate the need for a step-down transformer when operated on ahousehold power source or to require a step-down transformer having alow voltage ratio. Of course, elimination of the transformer altogetherprovides the least expensive system and also aids in the incorporationof a lint burning system into a conventional dryer. However, even theinclusion of a step-down transformer having a low voltage ratio hasadvantages over those systems in which the voltage source must bechanged by an appreciably high amount. Generally, dryers operate off 220v. lines and include both 220 v. and v. circuits and in practice, thecurrent carried by these lines is maintained within 15 amps. In order toprovide power for other components, it is desirable that the screen drawapproximately 11 amps. Accordingly, we have generally directed oureffect toward minimizing the current requirements of the lint burningscreen and more specifically toward approaching a current requirement ofapproximately 11 amps. Generally, we have found that a screen ofresistance-heated wire will require less current and consequentlyoperate off a higher voltage if a long strip is used with the parallelwarp strands individually connected across a voltage source so that eachof the strands acts as a parallel current path. Also, we have found thatin order to obtain a reasonable width screen and yet maintain a suitablepore size for entrapping lint particles, the woof strands must be of aconsiderably smaller mesh than that of the warp strands. In other words,the warp strands have been spaced farther apart and the woof strandsplaced closer together to give a rectangular pore approximating theentrapping characteristics of a square pore having a side dimensionsomewhere between the length and width dimensions of the rectangularpore. Also, it is advantageous to use a single woof strand woven backand forth through the warp strand. Since the warp strand which is alsoconnected across the voltage source provides an additional current path,the increased length increases its resistance to a point where it iseffectively a nonconductor. As is illustrated in FIG. 5, a long strip ofscreen 44 is connected across two conductors 46 and 48. The warpcomprises parallel strands 50 which act as separate current paths. TheWoof 52 is a single strand which is considerably longer than theindividual warp strands and is woven back and forth between them, withthe adjacent passes of the woof being much closer together than the warpstrands. This allows a larger spacing of the warp strands to maximizethe strip width with the closer woof passes minimizing the pore openingsof the wire to increase its lint entrapping capability. The long lengthof the single woof strand 52 makes it effectively a nonconductor so thatit does not appreciably affect the current flow through the parallelwarp strands 50.

In the foregoing description of a directly energized lint burningscreen, it was stated that the screen could be constructed so as to beable to be used in an available dryer circuit without a step downtransformer. A specific example of such a screen will now be given;however, while it must be borne in mind that other wire sizes,materials, lengths and meshes may be used, the example teaches theapproach to the ultimate screen construction which requires test andvertification due to unpredictable factors such as the transfer of heatby radiation from one warp strand to an adjacent one.

To cite a specific example, it has been found that a screen made from 35mil grade A resistance wire consisting of 80% nickel and chromiumrequires approximately 0.43 amp to bring it to the required temperatureto burn lint. Such a wire offers 53.06 ohms resistance per foot, andwhen approximately 57 /2 inches long offers a total resistance of 254.25ohms, which draws approximately 0.43 amp when placed across a 110 v.source. Since the total screen is drawing about 11 amps, this allows 26parallel wires which would theoretically draw 11.18 amps. We have foundthat given 26 parallel conductors to be used in a screen, we canconstruct a screen having a reasonable width and yet adequate lintentrapping capabilities by using 26 parallel warp strands spaced to theinch and interweaving the warp strands with a single woof strand spaced70 wires per inch (actually 70 passes per inch). This yields a screenstrip about 1% inches wide including the selvaged edge due to the singlewoof strand and 57 /2 inches long. The pore size produced by thedifferent mesh in each direction is sufliciently small to entrap lint.The resistance of the screen is 2.12 ohms per foot for a totalresistance of 10.16 ohms which draws approximately 11 amps and is heatedsufficiently to burn lint entrapped on it.

, Obviously any change in one of the dimensions of the screen requireschanges in the other dimensions. For instance, should a larger diameterwire be used, which would require more current per wire to bring it to adesired temperature, the number of parallel woof strands would have tobe decreased, the length of each woof strands may have to be changed andthe mesh in each direction probably altered. In some situations it maynot be practical to completely decrease the current requirements to avalue low enough for direct connection in a dryer circuit; however, insuch instances the current is reduced and thus requires less of a stepdown in voltage, which is likewise advantageous.

Returning to the screen assembly 26 detailed in FIGS. 2, 3, and 4, thisaspect of the invention will now be explained. While a directlyenergized screen comprising a long, narrow strip having a much finermesh in the longitudinal direction is suitable for entrapping andburning lint and in some instances without a step down transformer, thescreen, per se, is impractical for use in domestic dryers unless it canbe put into a suitable package size. Assuming a screen as dimensionedabove which requires no step down transformer, a package approximately 7inches square can be constructed as shown in FIGS. 2, 3, and 4.Basically, the idea is to wrap the long strip 44 on a frame 54. Theframe 54 comprises a sheet metal top 56, bottom 58, and two sides 60.Each side 60 has two spaced tabs 62 used to secure a side insulator 64to it. The top portions of the side insulators 64 have suitable cavitiesto receive the respective ends of a rod 66 which locates a top insulatorblock 68. The top insulator block 68 has a number of projections 70 onits front and back faces to receive and reverse the screen strip 44. Thepath of the strip 44 will be discussed below. Mounted adjacent the endsof the insulator block 68 are the connectors 46 and 48. Since both arethe same, only connector 46 will be described. The connector 46comprises body 71 with an upstanding terminal 72. Depending from thebody 71 is a clamping portion 74 which is reversed upon itself to clampthe end of the screen 44 insuring good electrical contact with each ofthe warp strands 50. It is important that the connector 46 clamp thescreen uniformly so that each woof stand makes electrical contact andthat the screen is not wrinkled or crimped so as to overlie itself. Asecond insulator block 76 rests atop the conductor bodies 71. The frametop 56 overlies the insulator 76 and is secured to the sides 60 by tabswhich extend through mating slots and are twisted or deformed. Both theinsulator 76 and the frame top 56 have holes through which the terminals72 project. 1

The bottoms of the side insulators 64 have suitable cavities for abottom rod 78, the ends of which are biased downward by springs 80. Abottom insulator 82 similar to insulator 68 is located by the rod 78. Aninsulator pad 84 and thermosetting plastic strip 86 are between portionsof the screen strip 44 wrapped around the bottom insulator 82, and theframe bottom 58 which is secured to the frame sides 60 by tabs in thesame manner as the frame top 56. The screen strip 44 has one end securedto connector 46 by its clamping portion 74. The strip continuesdownwardly to the bottom insulator 82 and is wrapped around it. In beingwrapped around the insulator 82, the strip is indexed a little more thanhalf of its width. The strip 44 continues upwardly to the top insulatorwhere it is again wrapped around and indexed. This wrapping is repeateduntil the opposite end of the strip arrives at connector 48 and isclamped to it. Once completed, the strip 44 presents four parallelportions or rows adjacent the front of the frame and four parallel rowsadjacent the rear of the frame. The back rows overlap the spaces betweenthe front rows and are spaced from the front rows by the width ofinsulators 68 and 82 which is about one-half inch. The space betweenadjacent rows is determined by the width of projections 70. We havefound about a quarter inch to be suitable. This spacing together withthe tautness of the strip produced by spring loading rod 78 prevents thestrip from shorting out on itself. The arrangement of the strip presentsthe least amount of nonscreened air passage which is a circuitous routebetween the indexed spaces between the screen rows.

The screen itself and the package described above are for use in thosesystems in which the lint laden air is caused to flow axially throughthe screen. In some installations due to space limitations, a radialflow pattern might be preferred; however, some of the same principlescan be applied. For instance, as to the package shown in FIGS. 6 and 7in which the lint chamber 122 is shown as a large square housing havinga smaller central outlet conduit 130in this case, the screen package 126comprises two frame members 132 secured together by four nut and boltassemblies 134. The frames 132 are spaced apart the width of the screenstrip 144 by a number of dowels 136, the ends of which are mounted inthe respective frames 132. The assembly includes a first connector 146to which the strip 144 is connected at one end. The strip continues fromthe connector 146 in a path which can best be described as a doublesquare spiral with the dowels 136 maintaining the path of the strip 144.The strip ends up and is secured to a second connector 148. Theconnectors 146 and 148 provide terminals for connection to a suitablepower source. In this embodiment, the right-hand frame member 132 issolid so that the lint laden air flows radially through the screen andout the outlet 130.

It should be understood, of course, that the foregoing disclosurerelates to only preferred embodiments of the invention and that it isintended to cover all changes and modifications of the example of theinvention herein chosen for the purposes of the disclosure, which do notconstitute departures from the spirit and scope of the invention.

We claim:

1. A lint filtering and burning screen comprising in combination:

a pair of spaced electrodes,

a plurality of warp strands extending between said electrodes in asubstantially parallel array, said warp strands having electricalresistance values which produce lint-burning temperatures when saidelectrodes are energized at a household voltage, said warp strands beingspaced part into a mesh too large to entrap smaller lint particlesnormally present in a clothes dryer eflluent or the like,

a single woof strand interwoven with said warp strands in a plurality ofpasses transverse to said warp strands, said woof strand having anelectrical resistance such that its influence on the characteristics ofsaid warp strands when energized is not significant, said woof strandpasses being spaced apart into a mesh which is finer than the mesh ofthe warp strands and which materially improves the lint-entrappingcharacteristics of the screen over a screen having a mesh in bothdirections equal to the mesh of said warp strands.

2. The lint filtering and burning screen as defined in claim 1 whereinsaid warp and woof strands are of the same material, wherein the mesh ofsaid warp strands is approximately 25 strands/inch and wherein the meshof said woof strand is approximately 70 passes/inch.

3. The lint filtering and burning screen as defined in claim 1 whereinthe length, diameter, number and material of said strands is such thatsaid screen draws approximately 11 amps when connected to a 110 voltpower source.

4. The lint filtering and burning screen as defined in claim 1 whereinsaid warp and woof strands are of a nickel-cnromium alloy, wherein themesh of said warp strands is approximately 25 strands/inch, wherein themesh of said woof strand is approximately 70 passes/ inch, and whereinthe length and diameter of said warp strands is such that said screendraws approximately 11 amps when connected to a 110 volt power source.

5. A lint filtering and burning screen assembly comprising incombination:

a frame having a pair of spaced electrodes,

an elongated resistance heatable wire screen strip connected to saidspaced electrodes adjacent its opposite ends, respectievly, said striphaving a plurality of warp strands in the longitudinal direction, saidwarp strands being spaced apart into a mesh too large to 6 entrapsmaller lint particles normally present in a clothes dryer efiluent orthe like,

a single woof strand interwoven with said warp strands in a plurality ofpasses transverse to said warp strands, said woof strand passes beingspaced apart into a mesh which is finer than the mesh of the warpstrands to improve the lint entrapping characteristics of the screenover a screen having a mesh in both direction equal to the mesh of saidwarp strands, said wire screen strip having sufiicient length so thateach of said warp strands is brought to the combustion temperature oflint when connected to a household power source without the additivecurrent carried by said warp strands being excessive, and

means to mount said strip on said frame in such a manner that the screendoes not touch itself.

6. The lint filtering and burning screen assembly as defined in claim 5wherein said warp and woof strands are of the same material, wherein themesh of said warp strands is approximately 25 strands/inch and whereinthe mesh of said woof strand is approximately 70 passes/ inch.

7. The lint filtering and burning screen assembly as defined in claim 5wherein the length, diameter, number and material of said strands issuch that said screen strip draws approximately '11 amps when connectedto a volt power source.

8. The lint filtering and burning screen assembly as defined in claim 5wherein said warp and woof strands are of a nickel-chromium alloy,wherein the mesh of said warp strands is approximately 25 strands/inch,wherein the mesh of said woof strand is approximately 25 strands/inch,wherein the mesh of said woof strand is approximately 70 passes/inch,and wherein the length and diameter of said warp strands is such thatsaid screen strip draws approximately 11 amps when con nected to a 110volt power source.

9. A lint filtering and burning screen assembly comprising incombination:

a rectangular frame,

a first insulator mounted in said frame,

an electrical connector adjacent each end of said first insulator,

an elongated strip of resistance-heatable screen secured adjacent itsopposite ends to said connectors, respectively, said screen comprising aplurality of warp strands in substantially a parallel array in thelongitudinal direction and a single woof strand traversing said warpstrands in a plurality of passes having a finer mesh than said warpstrand,

a second insulator in said frame substantially parallel to sadi firstinsulator, said strip being wrapped around said spaced insulators intotwo spaced layers, each layer comprising a plurality of parallel rowsspaced from each other less than the width of said strip,

indexing means on said insulators orienting each row parallel to eachother row and indexing the rows in one layer with respect to the rows inthe other layer with the rows in each layer overlying the spaces betweenthe rows in the other layers, and

means to maintain said strip taut.

10. The unit filtering and burning screen assembly as defined in claim 9wherein said warp and woof strands are of the same material, wherein themesh of said warp strands is approximately 25 strands/inch and whereinthe mesh of said woof strand is approximately 70 passes/ inch.

11. The lint filtering and burning screen screen as de fined in claim 9wherein the length, diameter, number 7 and material of said strands issuch that said screen draws approximately 11 amps when connected to a 10volt power source.

12. The lint filtering and burning screen as defined in claim 9 whereinsaid warp and woof strands are of a nickel-chromium alloy, wherein themesh of said warp strands is approximately 25 strands/inch, wherein themesh of said woof strand is approximately 70 passes/ inch, and whereinthe length and diameter of said warp strands is such that said screendraws approximately 11 amps when connected to a 110 volt power source.

13. A lint filtering and burning screen assembly comprising, incombination:

an electrically insulated frame having spaced end plates with a pair ofspaced electrodes and a plurality of dowels arranged in a double spiralextending therebetween,

an elongated resistance-heatable wire screen strip connected to saidelectrodes adjacent its opposite ends, respectively, said screen striphaving a plurality of warp strands in the longitudinal direction, saidwarp strands being spaced apart into a mesh too large to entray smallerlint particles normally present in a clothes dryer eifluent or the like.

a single woof strand interwoven with said warp strands in a plurality ofpasses transverse to said warp strands, said woof strand passes beingspaced apart into a mesh which is finer than the mesh of said warpstrands to improve the lint entrapping characteristics of the screenover a screen having a mesh in both directions equal to the mesh of saidwarp strands,

said wire screen strip being mounted on said frame and guide by saiddowels into a double spiral configuration so that the wire screen stripdoes not touch itself and has a sufficient length so that each of saidwarp strands is brought to the combustion temperature of lint whenconnected to a 110 volt power source, and

said warp and woof strands having a length, diameter number and materialsuch that said screen strip draws approximately 11 amps when connectedto said source.

References Cited UNITED STATES PATENTS 1,733,116 10/1929 Coups 2458 X2,063,663 12/ 1936' Downward.

2,412,843 12/ 1946 Sparagen 219-545 2,496,279 2/ 1950 Ely et a1 338-20 8X 2,522,542 9/ 1950 Schaeffer 338-208 X 2,912,661 11/1959 Balestrini338-316 X 2,984,357 5/1961 Kuiferath 209-238 X 3,061,942 11/1962Schofield 34-82 3,268,080 8/1966 Eberly -428 X 3,344,257 9/1967 Moeller338-208 X 3,408,794 11/ 1968 Stoddard 55-282 OTHER REFERENCES 8,398 4/1897 Great Britain.

ANTHONY BA'RTIS, Primary Examiner US. Cl. X.R.

2 2 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,541, 303 Dated November 17, 1970 Inventor(s) Thomas J. Brinkman,Thomas H. Fogt, and Charles C.

Whistler, Jr. It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

a o Column 1, line 47, "line" should read --lint--; Column 2, line 44,"Whitler" should read --Whistler;

line 66, "effect" should read effort-: Column 3, line 44, "amp" shouldread --amps--;

line 48, "amp" should read -amps-; line 70, "strands" should read--strand-.

In the Claims: Claim 4, line63, "nickel-enromium" should read --nickelchromium--; Claim 5, line 9, "direction should read -directions--: Claim8, lines33, 34 and 35, delete "appriximately 25 strax inch, wherein themesh of said woof strand is"; Claim 9, line 53, "sadi" should read-said-:

line 61, "layers" should read -layer--; Claim 11, line 69, delete"screen", second occurrence; line 72, "10" should read --llO--; Claim13, line 18, "entray" should read -entrap--;

line 29, "guide" should read --guided--.

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